Mesenchymal stem cells (MSCs) can be isolated not only from tissues of adults, such as bone marrow, fat, a synovial membrane, an alveolar bone, and a peridontal membrane, but also from various cells, such as placenta, cord blood, and umblical cord. In addition, the mesenchymal stem cells can be cultured and proliferated in vitro. Furthermore, the mesenchymal stem cells have multipotency so that the mesenchymal stem cells can be differentiated not only to a plurality of mesenchymal cells (osteoblast, fat cell, cartilage cell), but also to non-mesenchymal cells (neural precursor cell, hepatocyte). Accordingly, the mesenchymal stem cells are expected to be applicable as a cell source for regenerative medicine and cell treatment.
A medium containing fetal bovine serum (FBS) has been conventionally used for culturing mesenchymal stem cells. Bovine serum has lot differences, and in addition, causes an immune response in transplantation because the use of bovine serum results in contamination of the mesenchymal stem cells with a serum protein derived from a heterozonic. It is difficult to stably culture the mesenchymal stem cells even by use of human serum due to individual differences. Further, this culturing gives a large physical burden to a donor, and costs a large amount of money.
Therefore, it is known that, in order to supply mesenchymal stem cells which are safer and has a stable quality, a serum-free medium with which no or little contamination with a protein derived from a heterozonic occurs during culturing is suitable. That is, it is preferable that the mesenchymal stem cells are proliferated by a serum-free culturing. Patent Literature 1 and Non-patent Literature 1 disclose serum-free culturing of mesenchymal stem cells. The serum-free culturing mesenchymal stem cells as described in Patent Literature 1 and Non-patent Literature 1 produce a proliferation promoting effect superior to that of culturing of mesenchymal stem cells with a 5 to 15% FBS-containing medium. Such serum-free culturing also allows to produce mesenchymal stem cells whose multipotency is maintained (improved).
It has been known that mesenchymal stem cells not only have low immunogenicity, but also affect functions of various immune effecter cells (T cell, B cell, NK cell, dendritic cell) (see Non-patent Literatures 2 to 5). Accordingly, the mesenchymal stem cells are expected to be applicable to treatment for various diseases relating to immune responses (Non-patent Literature 6). Non-patent Literature 7 discloses that mesenchymal stem cells down-regulate proliferation of T cells caused by a mouse mixed lymphocyte reaction (MLR).